Abstract : The use of low-density cellular concrete, having an oven-try unit weight of 50 pcf or less, as a backpacking material for deeply buried protective structures was studied. Cellular concrete was found to be suitable for this type of application. A number of physical properties of cellular concrete were determined to provide input to design codes. Constrained compressive crushing stress levels from 20 to 1,000 psi for slow rates of loading were observed. Rapid-loading tests and equation of state measurements were also made to determine the rate sensitivity of the concrete. Compressional wave velocities from 2,000 to 6,000 ft/sec were also measured. Modulus of elasticity values from 20,000 to 220,000 psi were measured for concretes in the as-cast condition with respect to moisture. Flexural strength to compressive strength ratios from 0.16 to 0.33 were observed. Early age stiffening characteristics of cellular concrete were also studied. Some design procedures based on the data analysis are suggested. Some possible areas of difficulty during prototype use of cellular concrete as a backpacking, such as lift heights, cold joints, temperature problems, and water-saturation problems, are also explored. (Author)